Magnetic core shift register circuit



Jan. 26, 1965 .1. W. sEDlN ETAL 3,167,749

MAGNETIC CORE SHIRT REGISTER CIRCUIT Filed July 29, 1959 /huw' ALT@ ATTO R N EY! 3,67,749 MAGNETEC CORE SHFT REGSTER CERCUH James W. Sedn, Los Altos, aiif., and Robert E. Wesslund, St. Paul, Minn., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy' Filed July 29, 1959, Ser. No. 830,441 7 Claims. (Cl. 340-174) This invention relates to magnetic core register devices, and more particularly to an improved register circuit of the type employing magnetic cores. Y

Magnetic cores otter certain advantages when used as storage, logical and memory devices in electronic data handling systemsv since they are. small, require low-operating power and 'can store information for extended cores due to the fact that the cores may be magnetically saturated in either -ot .two directions and after the force -United States Patent periods of ktime without subsequent power input and loss i Y in standing.' Binary datay caribe stored by these magnetic i. creating the saturation is removed, a' remanent tlux exists 4 Within the core Whose direction is dependent on the direc- 5- tionof the last applied magnetomotiveforce. The magi.

netic saturation is accomplished by passing-*a current pulse 'i through a winding on the core.

Progressively moving information from the input circuit to the output' .circuit along'a chain formation of magnetic cores at a selected rate and at a selected time defines the operation andthe function'of a shift register or as it is sometimes known, a magnetic delay line. This information transfer or switching is achieved bygv plicatio'n of a current pulse to a winding onthe magnetic "core, usually referred toas the advance or drive wind-f ing, so as to' produce aremanent flux within the core v ofa direction opposite tothe pre-existingtiux directiont During the change in the flux direction,-a voltage pulse is attinge Fatented Jan. 26, i965 succeeding core. However, even though the preceding,

core is: not saturated, nor is its residual tiux direction changed, the undesired voltage that appears across the *output Winding of the preceding core with the aforemen tioned blocking or decoupling circuit, a suiiicient magnetomotive force is generated to alter the magnitude oi the residual flux and, thereby prevent its assuming the ux condition corresponding to one or the other of its stable states. It is this slight change in residual flux that vdecreases the' signal to no signal ratio and accounts for one of the main difficulties in the prior art circuitry.

An object of this invention is to provide anA excellent magnetic ycofre' shift registry circuit, which Will have a relatively high signal to no signal ratio and maximum stability of operation.

Another object is to provide anelectrically simple, practical, eiiicient, inexpensive and stable magnetic core shift register circuit.

, Other objects and advantageswill be apparent tromthe following description of an embodiment of the in-` vention, and the novel features thereof will be particularly inducedvin/anoth/er winding,`namely the output Winding@ l 'lfhe voutput-Winding is connected to a Winding on the Vcore of the next succeeding magnetic core in the chain .and

the pulse4 produced acrossthe output'winding of the n first core will be applied to the input Winding ofthe next succeeding core. If thisinduced voltage pulse isn-greater than acertain selected value,it will produce la magnetomotive force on the second core sutiicientto change v the Vresidual tiuxdirectionj of the second core, provided,

howeventhat the'forcecreates a flux oppositein direction to the remanent flux existing on the second core before the applicationpof the induced voltage. yIt should be noted thatWhere the saturationV current is applied to produce a iiux in the same direction as the residual flux already existing on the core, the iiuxV change' thuslypro-V duced is smallland hence the voltage induced at the output Winding of that core is less thantheininimum required to saturate the next succeeding core.

Sincefiri operation, the information or data is transferredfrom 'one core tothe" next, eachvcolremust have -k an advance winding which, when a current pulse is lap- Vplied to it, saturates'the core in 'one direction invorder lto .advance theinformation toivard' the output. advance pulse creates a flux saturation' opposite in polar`v ity to that existing' in the coreV before its application, an

ing and the input Winding ofzthatcore. Since the output winding of one core is connected to the input winding of the next corethis induced voltageat the input winding' will be'coupled back to the output Vwinding of the precedv ing core and produce therein undesirable results. 'In order to overcome thiseffect-, an asymmetric'ally.conductive' device may be shunted across the input winding ofa core and this'shunt device inconjunction Withla similar deviceY series connected between the input'fwinding of one core pointed out hereinafter in connection with the appended claims. f 'n FG. 1 is a' graph, somewhat idealized of the hysteresis' loop'for a magnetic material used in the `fabrication of magnetic coresgk,

FG. 2 is a schematic diagram o f a magnetic core shift register circuit` before this invention is appliedltheret EIG. 3fisa schematic diagram of animproved magnetic core shift register employing the embodiment of this invention. i

ylViagnetic memorycores are fabricated from magnetic "materials, as for example, molybdenum-permalloy or manganese-magnesium ferrite, which 'exhibit the desired hysteresis loops as illustratedV in FIG. 1.` The magnetic Aproperties of each core used inpshift registers core charf acterized by the loop. of FIG. 1,; wherein .the horizontal axis represents the magnetizing force H applied to the core and the vertical axisrepresents the flux density B. Bm is the maximum value of the fiux density in the core during "the application of a"saturating rnagnetor'notivepy force, While Br is the remanence `iiux density Vto whichy the induction returns whenthe magnetomotiveforce is removed.'V The coercive force Hc is the magnetizing force required'to return the core to zero magnetic induction after ,the application oa saturating magnetomotive force 5O. inv the 'oppositefdirection lt should be noted that two f stable magnetic states exist for the core and they'occur at the intersection of thehysteresis loop andthe vertical B. axis, that is, Where the magnetomotive force is removed or equalgfto Zero after theV applicationV of a saturating magnetomotive force. A large positive magnetizing force or pulse will leave the core with a positive If the voutput voltage pulse is inducedon both Vthe output Wind-v i andthe output Windingy of the preceding. core, are suf-v Winding Na or Nb.

remanent or residual magnetism asrepresented by the state l ,While a similarlvlarge negative magnetizing pulse will leavetheucore inthe state `represented by 0. This bistable characteristic of .the core makes it possibleto store a'binary digit or information... f-

j TheV illustrated magnetic core shift register ordelay y line' comprising a chain formation .ofsubstantially iden? I tical magnetic core is illustrated in FIG.v 2, whereinfour.

cores are shown, though more or less cores may beem-A ployed. The ocres may be olf any suitable cross-sectional shape, preferably toroidal, each core having Wound thereon three separate and distinct vvindings,which are an input winding N1, an output Winding No and an advance f The advancefwindings NEL and Nb are l provided on alternate cores in the chain and altern-ate windings are A,connected in of alternate coresfbeing joined s o `Vthat the even core ad- Y Vance windings Nb arein, series with each other, and 4the i -Ni ofthe succeeding core andthe resistor 6., The ad- 'Vance windings Na and Nb are lWound. around the cores ,y Vrnost conimonly empioyedtirnefcycle, that is',` one'l in which the signal inputV occurs` at- ,the saine timeas i2 advance y r` t putwin l odd core advz'inceV windings 'Na are sei'ieswitia 'each other, and each 'grouprof alternatefadvance windings,r be v5 j ,ing pulsed independently of the-other group. The first 1 core ,of the chain Yreceives the external input pulse applied acrossV its'inputwinding Ni.- Eachfcore output'winding v No is connected vto the input winding kof the next succeed,-

Vtive devicesuch as a diode or rectiiier 5 and a resistor e, with `a second diode 7 in shunt across ythe input Winding iinV 'such a direction as to 'energize the corespto the=0v state 15 fof magnetization when rectangular current pulses are `ape vplied tothe advance circuits Sande). f

Initially alljthe cores arevinthe 0 statefandbtheiirs-t n ,pulse to appear in time is theez'l, ladvancepulse which merely creates in the Vvodd cor'esfrnagnetization vfrom' 50i 20 to '-Bm. lSince this isia vrelatively,small chan-gein iiux only :a small voltage-will bed-eveloped cn'the output windl A'ings of `the odd 'coreswhich is of an insuiiicientmagnia 'tude to aiect the flux`.1state of thefnext succeeding core Y. lto which itisccupled.

` The signal input toltheriirst core'inay occur at anytime L other than in coincidence with the advance pulse ik, The

Vpulse, is asshown in'FIGQ =2. The input'winding N1 of each core Yis wound in a direction so chata positive inputv Iiiulse Iof. ,suticient'rnagnitude will energize, the` core to' the lwmagnetic state'.-An input signal is now appliedto'the f Nifwindingsto corel-and Vthe core'changes fr0-n 30 to Y i state ofinagnetization.' This rapid changefoffiiux in 4core i induces a voltage acrossthe outputwindingsjof that. core; which voltage tendstodrive a cur-rent `toyvardjthe inputwindingNi of core 2 inthe*direction'off4 high resis't-A Y.

ance through diodeso thattthe cu'irentreachingItlie j ingut windings N if core 2 is oan injsuicient'n'iagni'tude to change the ,niag'neticustate of core 2gv,Adxnince-pulseY. 'K ,i2 now occur`s, but, sincejthe-even coresware'iin thelO state they-remain,inA thatstatetand no change occurs.:

vThe next 'pulse to appear/'in `the ,time .cycle is; advance pulse i1, *Whichienergizes core ifromwitsi previous ffl 'Y state to theO state ofuniagnetization. K'Thisfrapidiiux change,V induces av Voltage-,across the `output WindingN,

of `thatfcore in' thefdirectidn-pf loyvresistancef cir-*forward* g n :propagation througlidioder and the. resultant current intlse thereby applied'io theinput winding. Nyon?k core .2"Y V'drives theicoreztromljf state tothe l state'of inage neti'zation.k .Advance'pulse izmsirnilarly advances th'efl" state from Vcofre 2 "to corey 3, Land,advance pulse. i1 ,there i untill-v1 theputputstageisgreacled.' l t. Y

it shouid' b e noted thatthe'fvoltagef induced'in thel in- Lng o-f'anycore, asfofrleiranfipleycore; when`VV Vthe colexniagnetization state is changed V.from l to 90; by the advance.'pulsefim drivesl lcurrent in a-f'orward prci'iagatingr, mannery through' `diodeY Stowards the output L winding YNojof,thepreceding core.' Thisbaclclcurreutiis kless is altered and the resultanttchange. follows'the hys;

'included inthis shurit circuit to dissipate thisenergy vand l itc introduce some impedancein thisfportionf-'of the .cf

ina' directionto drive the preceding .core to theg1l?"-state but}di-ode, 7 Whichzlis yin shufnt acrosslthe input*vvir'idingrr N, short Ycircuits a portion of'this ,backY signal. AResistor 6 is 'cuit'.`V Thevmagnetic state of` the preceding coreV nevertli 4tieslw'ith magneticcore shit'registersn. Y

'H5 and, then falls backalniosrallithe Waytothe fGstate 70 again.Y The `fact that' itdoes not; fall-allv therway back,''

andltherefore .causes :aslight algebraiclincreasetin kthe signalf'to no signalgratio? is one of the main dicul ing core inV the chain the yugh an` asymmeztrically conduc-- l0 L it ,has been* found' 'that the addition ,offthese extrarwindings Y v to buck cnitlthe;back;signa-l,v increases',thenper'ational i' storing Scores 's'tably'iinagne'tizableV selecti/el 7 the first core; connected 'i it ist,connected,z v rneans. conneoted'wwitlifachfset threek seriesl connected Windingsgand cooperating the otherwindings on the same core opposes any back signal from the input Winding of anyvcore4 after the first one which tends to be set up inWindingjNoonthe precedingV core. It now'lvhowever,,becomes necessaryV to increase the numberfoffturns ot theinput .windingV Ni to forni ak larger Winding Ni: onall cores after-thc til-st one, in order `that^theftotalsignal 4being advanced from a preceding coreztoV the nextscorein theffchainislnot diminished by:

. the opposingv added windings -Nmwhichfinight otherwise `prevent sufficient magnetizationof the `next core toefeot;

ma. changev ofitsfinagnetic state; r itil-llasbeen found satis@v factory :to make such'fan increase inthe total numberof turns ot'theN, input Lwix'idinfg by anv aniountequal'tothe turns ,ikn'thefadditional Winding NmsoM that' the resultant magnetizing. signedy received, forexarnple, =frorrifcoreY Il'jby coreZfisthe same as before the addition of the Nm Wind- Vingsij The turns Athat were added'tothe,inputlyvindingN Tof f to give,windingNfdo'notvthemseives produce vinding7 l N5, which an` additionalgvoltage at the outnu -1 mightcancel-outfall'thc desirable effects introduced by the 'new`\vinding N511 since ytheir induced .voltages are in o position,- because any'iadverse voltagesLinducedgacross theadditional;turns on' Ni" arefshunted across Winding Nbydiode 'j vv'iiiehjis connected actos' the'totalWind-r` .ings Ni. Since the voltagelinduced 'acrcsslthe additional winding Nmis not shuntedgtlie, etgainor .irnp'roi/erneutV inl"-signal tofnov signal ratio isapproximately;propel tional Within liniits vto die-*vcitagexacross lWinding Nm.

Y lity ofA thev shift' Vregister and'eirjicreases',A 0v signal ratio by 'at least- 6: l.

f tails; rn

fas `expressed in the appended clainis: v

We claire: A f i "1.1 Atshiftf registencomprising a chain. fot inormation 1- r'ieachlot.

twodirections,'input;outputfgan Y y tpunwindingof eachicore except the nected inputj Windingf onfthe directionl to oppose Lthefsaid input-'winding with blocking win ifngfor vbiocking-the'transfer oenergy from hevotpli't W' 'is nr seriesY out insuiicient Vtion of thecorejon which preceding vcore Wit-li `whichy to prevent ach-ange. inv magno the blocking winding is located:

' 2."The register .accordingtolclainif fmeansfincludestone -rectifying means, `in .seri

input Winding.

t information' storing' coresy stably linagnetizable; selectivlyV vof directio.ris with j input, foutent-and fads/anceY in the embodiment ofthis invention, as lillustratedin f loe understood Athativarious Ychanges inthe'fdc aterialsandarrangeinents vof'partn Vwhich ,have t beenthereiny described andlillnstrated lin order ltoexplairi Vthefnatuie of this invention, may be,nuade(bytiietskilledv Y inthe art within .thea i rincipleandnscope; ot :thefinvention windings pn;

dthecutpnt" l winding on` the, vprecedingl corefandfi'iavingiturnsin1 which l offsaid ih sad' ring lon "the snow-as windings on each core and with the output winding of each core except the last, connected in series with the input winding of the next successive core, with one rectifying means in series with both series connected windings and another rectifying means in shunt across the input winding that is in series with the output winding, that improvement which comprises a blocking winding on each core after the first core, `connected in series with the output winding on the precedingcore and the input winding on the same core, and `in series with said one rectifying means and having 'turns in a direction and in number to block the transfer of energy from said input winding back to :the output Winding on the preceding core with which it is in series, but permitting a change in magnetization of the core on which the input and blocking windings are located in response to a pulse signal from the output winding of the preceding core.

4. in a shift register of the typel having a chain of information storing cores stably magnetizable selectively in each of two directions with input, output and advance windings on each corey and with the output winding of each core except the' last, connected in series with the input winding of the next successive core, with one rectifying means in series with both series connected windings and another rectifying means in shunt across the input winding that is in series with the output winding, that improvement which comprises winding means responsive to current low between each output winding and the input winding with which it is in series, for blocking the transfer of energy from said input winding back to the output winding with which :the input winding is connected, but ineffective to prevent a change in magnetization of `the core having said input winding.

5. In a shift register of the type having a chain of information storing cores stably magnetizable selectively in each of two directions, each core having an input, output and advance windings, the input winding of each core after the first and the output winding of the immediately preceding core of the chain beginning with the first core being in series circuit, and wherein asymmetrically con-- ductive elements are operative on the series circuit for forward signal propagation and another asymme-trically conductive element in shunt with said input winding to substantially block transfer of energy from the `input winding of the succeeding core back to the output winding of rthe preceding core in response to change in magnetization of the core supporting the input winding, the improvement which comprises a back-signa blocking winding supported on the same core as said input winding after the iirst core wound in opposition to said input winding and connected in series with said input winding between the output winding of the preceding core and said shunting asvrnrnetrically conductive device, and having a number of turns to allow a change in magnetization of the core on which said input and said blocking windv ings are located in response to a puise signal from the output winding of the preceding core, but having turns to block the transfer o'f energ,J from said input winding back to the youtput winding of the preceding corre not otherwise shunted by the asymmetrieally conductive element.

6. in a ,shift register of the type having a chain of information storing cores stably magnetizablc selectively in each of two directions, input, output, and advance windings on each core and having Ni, No, and N turns respectively, that improvement for each core after the iii-st, which comprises a iirst loop circuit having in series connection therein the output Winding ofthe preceding core, one rectifying means, said input Winding, Nm additional turns on said input winding, and a blocking winding having Nm turns in a direction to oppose said input winding, and wound on the same core, a second ioop having in series therein said input winding and additional turns and another rectifying means whereby the transfer to the output winding of the preceding core of the voltage induced across said input winding andkadditional turn will be blocked, but any voltage induced on the output winding the preceding core will be transferred to said input winding.

7. The improvement according to claim 6, wherein said second loop also contains in series connection therein a resistance element. i

References Cited 'by thelExaminer UNITED STATES PATENTS 2,825,890 3/58 Ridler 340-174 2,851,677 9/58 Crooks 340-174 2,863,138 12/58 Hemphill 340-174 2,886,799 5/59 Crooks 340-174 2,911,621 11/59 Crooks 340--174 2,911,626 1l/59 IOnes S40- 174 2,930,029 3/60 lvioore 340-174 3,040,302 6/62' Dumaire S40- 174 i IRVING SRAGQW, Primary Examiner.

EVERETT R. REYNGLDS, JOHN T. BURNS,

' Examiners. 

1. A SHIFT REGISTER COMPRISNG A CHAIN OF INFORMATION STORING CORES STABLY MAGNETIZABLE SELECTIVELY IN EACH OF THE DIRECTIONS, INPUT, OUTPUT AND ADVANCE WINDINGS ON EACH CORE, THE INPUT WINDING OF EACH CORE EXCEPT THE LAST CONNECTED IN SERIES WITH THE INPUT WINDING OF THE NEXT SUCCESSIVE CORE, A BLOCKING WINDING ON EACH CORE AFTER THE FIRST CORE, CONNECTED IN SERIES WITH THE SERIES CONNECTED INPUT WINDING OF THE SAME CORE AND THE OUTPUT WINDING OF THE PRECEDING CORE AND HAVING TURNS IN A DIRECTION TO OPPOSE THE SAID INPUT WINDING WITH WHICH IT IS CONNECTED, MEANS CONNECTED WITH EACH SET OF SAID THREE SERIES CONNECTED WINDINGS AND COOPERATING WITH SAID BLOCKING WINDING FOR BLOCKING THE TRANSFER OF ENERGY FROM SAID INPUT WINDING BACK TO THE OUTPUT WINDING ON THE PRECEDING CORE WITH WHICH IT IS IN SERIES BUT INSUFFICIENT TO PREVENT A CHANGE IN MAGNETIZATION OF THE CORE ON WHICH THE BLOCKING WINDING IS LOCATED. 